Tooling for sheet metal forming apparatus

ABSTRACT

The female die in a sheet metal brake is fitted with TEFLON inserts at critical points in the die, which inserts permit the sheet metal to move relative to these inserts without exhibiting the usual tendency to mar the associated surface of the sheet metal. The inserts are preferably circular in cross section, having active segments which engage the metal workpiece during the forming process. The female die defines semi-circular cavities for rotatably receiving these cylindrical inserts or rods, and this configuration assures that the wear of the rods occurs uniformly around the periphery thereof, these rods being adapted to rotate incrementally during each forming operation of the associated male member so as to present an adjacent segment of the periphery of the TEFLON rod to the next succeeding workpiece.

[ 51 Oct. 28, 1975 TOOLING FOR SHEET METAL FORMING APPARATUS [75]Inventors: Richard N. Gillette, East Hartford;

Robert H. Sand, Canton, both of Conn.

[73] Assignee: The Vulcan Radiator Company,-

Hartford, Conn.

22 Filed: June 4, 1973 21 Appl. No.: 366,632

[52] US. Cl. 72/212; 72/380; 72/386 [51] Int. Cl. B21D 9/08 [58] Fieldof Search 72/380, 386, 212, 213; 29/132, 110

[56] References Cited UNITED STATES PATENTS 419,156 1/1890 McGiehan72/212 600,699 3/1898 Weber l 72/213 1,552,416 9/1925 Bingham... 72/2132,669,891 2/1954 Ware 72/213 2,908,315 10/1959 Hellwig.. 72/2133,500,679 3/1970 Smith 72/212 3,613,427 10/1971 Haddon 72/212 FOREIGNPATENTS OR APPLICATIONS 68,127 3/1969 Germany OTHER PUBLICATIONS CastNylon Tooling-Better Than Metals?, Tool &

Mfg. Engineer; Vol. 49, No. 6, Pgs. 78-80; 12/1962; C. W. Dames, .lr.

Primary ExaminerC. W. Lanham Assistant Examiner-James R. Duzan Attorney,Agent, or FirmMcCormick, Paulding & Huber [57] ABSTRACT The female diein a sheet metal brake is fitted with TEFLON inserts at critical pointsin the die, which inserts permit the sheet metal to move relative tothese inserts without exhibiting the usual tendency to mar theassociated surface of the sheet metal. The inserts are preferablycircular in cross section, having active segments which engage the metalworkpiece during the forming process. The female die definessemicircular cavities for rotatably receiving these cylindrical insertsor rods, and this configuration assures that the wear of the rods occursuniformly around the periphery thereof, these rods being adapted torotate incrementally during each forming operation of the associatedmale member so as to present an adjacent segment of the periphery of theTEFLON rod to the next succeeding workpiece.

3 Claims, 5 Drawing Figures US. Patent' Oct.28, 1975 Sheet1of2 3,914,972

FIG

SUMMARY OF THE INVENTION This invention relates to metal forming, anddeals more particularly with a die construction which has application tothe bending of sheet metal, one surface of which sheet metal must not bemarred or scored. This requirement is one which has become quitesignificant in the forming of polished aluminum, and also in the formingof vinyl clad sheet metal. The present invention may, therefore, beapplied to cold forming sheet metal with at least one surface which mustnot be marred. A female die is provided for engaging this particularsurface of the sheet metal workpiece when the invention is utilized in aconventional sheet metal brake. However, the invention might also beadapted for use in a forming process where the workpiece is rolled orotherwise formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view partly insection showing a sheet metal workpiece in place between the mating maleand female die members.

FIG. 2 shows the female die without the workpiece or the male dieassociatedtherewith.

FIG. 3 shows the female die with the workpiece prior to being formed,and with the male die being spaced from the female die.

FIG. 4 shows the apparatus of FIG. 1, and

FIG. 5 shows the configuration of the resulting workpiece after havingbeen formed in an apparatus of the present invention.

DETAILED DESCRIPTION Turning now to the drawings in greater detail, FIG.1 shows a male die of conventional construction being fabricated fromsteel and adapted to engage one surface of a sheet metal workpiece W andto form the workpiece into the desired shape dictated by the cooperatingsurfaces of a mating female die member 12 associated therewith.

FIG. 2 shows the female die in vertical cross section as including asteel block 14 having a clearance cavity 16 formed in the block for thepurpose of receiving the male die 10.

The female die 12 further includes spaced lands 18 and 20 whichcooperate to define the boundaries of the clearance cavity 16, and whichlands receive the workpiece W as best shown in FIG. 3, prior to theforming operation. These lands 18 and 20 are preferably not fabricatedfrom the same material as is the block 14, namely from steel, but areinstead fabricated from an anti-friction material such as a syntheticthermoplastic material selected from the fluorocarbon group whichincludes polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE) andtrifluorochloroethylene (Kel-F) sold under the tradename TEFLON or thelike.

In further accordance with the present invention these spaced lands ofsynthetic thermoplastic material are provided with a circular outercontour or periphery and are free to rotate in cavities defined for thispurpose in the female die 12. As best shown in FIG. 1 each of theselands are defined by longitudinally extending rod members 18 and 20 eachof which is rotatably received in the female die but can be removed forreplacement or repare by means of the screws indicated a generally at22, 22. Thus, the semi-circular cavities 24 and 26 which rotatablyreceive the rods 18 and 20 are defined in part in the body portion 14 ofthe female die and in part by longitudinally extending retaining strips28v and 30 respectively. As so constructed and arranged the frictionalforces exerted on these TEFLON rods 18 and 20 during the formingoperation depicted in the FIG. 3 and FIG. 4 views will cause limitedangular rotation of the rods as indicated generally at 32 and 34 in FIG.4. This limited rotational movement of these rods precludes excessivewearing being caused to the rods at any one segment of their periphery,and assures that an anti-friction surface will be presented to theunderside of the sheet metal workpiece W during the entire formingprocess. The clearance cavity 16 of the female die 12 is such that theunderside S of the workpiece W never contacts it during this formingprocess. Thus, the workpiece W and more particularly its non-mar surfaceS never contacts the metal componets of the die construction, andinstead always contacts only the TEF- LON rods 18 and 20 during theforming operation.

The advantages to the foregoing die construction will be readilyapparent to those familiar with the art of forming sheet metal. Whilethese advantages can be realized in adapting a die of the type shown inthe drawings to a sheet metal brake of conventional construction, theseadvantages will be particularly apparent when the workpiece has onesurface in particular which must not be marred or scored by the die.More particularly, this die has particular advantage in the art offorming sheet metal enclosures of the type used in the heating andventilating industry where these sheet metal components are fabricatedfrom a vinyl clad material or from a polished relatively soft aluminummaterial. However, the advantages to the present invention can also beapplied to the forming of any metal components and might be well adaptedfor use in the forming of prepainted or precoated sheet metalworkpieces.

We claim:

1. An apparatus for bending sheet metal panels with a non-mar frontsurface and comprising:

a. elongated male die means for impacting the rear surface of the panel,

b. a female die means engageable with the non-mar front surface,

c. said female die means having a rigid body portion defining aclearance cavity for the panel portion to be bent and spaced landsextending longitudinally on either side of said cavity,

(17 at least one of said elongated lands being more particularly definedby a longitudinally extending member of synthetic material selected fromthe thermoplastic fluorocarbon group which includespolytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE) andtrifluorochloroethylene, and

e. said synthetic member having a circular cross section and beingmounted in a semi-circular cavity defined by said rigid body portion sothat said synthetic member is free to rotate during the bending of suchsheet metal panel.

2. The apparatus of claim 1 wherein said female die means includes asecond synthetic member of circular cross section mounted in a secondsemi-circular cavity associated with the other of said spaced lands insaid rigid body portion, said second synthetic member also selected fromthe fluorocarbon group which includes polytetrafluoroethylene (PTFE),tetrafluoroethylene attached to said cavity defining body portion andcoop- (TFE) and mfluorochloroethylene' erating therewith to define andcircular cavities to re- 3. The apparatus of claim 2 wherein said femaledie means further includes a rigid retaining strip for each of saidsynthetic members, said strips being removably 5 strict said members torotational movement.

1. AN APPARATUS FOR BENDING SHEET METAL PANELS WITH A NONMAR FRONTSURFACE AND COMPRISING: A. ELONGATED MALE DIE MEANS FOR IMPACTING THEREAR SURFACE OF THE PANEL, B. A FEMALE DIE MEANS ENGAGEABLE WITH THENON-MAR FRONT SURFACE, C. SAID FEMALE DIE MEANS HAVING A RIGID BODYPORTION DEFINING A CLEARANCE CAVITY FOR THE PANEL PORTION TO BE BENT ANDSPACED LANDS EXTENDING LONGITUDINALLY ON EITHER SIDE OF SAID CAVITY, D.AT LEAST ONE OF SAID ELONGATED LANDS BEING MORE PARTICULARLY DEFINED BYA LONGITUDINALLY EXTENDING MEMBER OF SYNTHETIC MATERIAL SELECTED FROMTHE THERMOPLASTIC FLUOROCARBON GROUP WHICH INCLUDESPOLYTETRAFLUOROETHYLENE (PTFE), TETRAFLUOROETHYLENE (TFE) ANDTRIFLUOROCHLOROETHYLENE, AND
 2. The apparatus of claim 1 wherein saidfemale die means includes a second synthetic member of circular crosssection mounted in a second semi-circular cavity associated with theother of said spaced lands in said rigid body portion, said secondsynthetic member also selected from the fluorocarbon group whichincludes polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE) andtrifluorochloroethylene.
 3. The apparatus of claim 2 wherein said femaledie means further includes a rigid retaining strip for each of saidsynthetic members, said strips being removably attached to said cavitydefining body portion and cooperating therewith to define said circularcavities to restrict said members to rotational movement.